Jitter tracking anti-spoofing algorithm

Abstract

A system and method to distinguish spoofing signals from true GNSS signals is disclosed. One aspect of the present invention combines measuring GNSS carrier signals with measuring jitter in a vehicle's position via a low-cost inertial measurement unit (IMU) to distinguish spoofing signals from true GNSS signals. The present invention employs natural and/or artificial jitter of a vehicle, that, when combined with a tightly coupled inertial navigation system (INS), allows the receiver to distinguish the spoofing GNSS signal from the true GNSS signal. This spoofer survivability algorithm may be implemented, for example, in the software of a GNSS (or GPS) navigation system.

The invention claimed is: 
     
       1. A method comprising the steps of:
 detecting a plurality of Global Navigation Satellite System (GNSS) carrier signals; 
 temporally tracking characteristics of the plurality of GNSS carrier signals for dither, thereby creating dither data; 
 comparing the dither data; 
 identifying at least one falsified GNSS carrier signal based upon a degree of correlation of the dither data; 
 temporally tracking the plurality of GNSS carrier signals, thereby creating signal source data; 
 filtering the signal source data to remove multipath signals; 
 binning the remaining signal source data into signal sets; and 
 determining one or more signal sets that produce a corresponding internally consistent position according to a cost function based on a consistency of a corresponding position, wherein each one of the determined signal sets corresponds to falsified GNSS carrier signals or true satellite-transmitted GNSS carrier signals; 
 wherein further processing of each of the one or more signal sets that produce a corresponding internally consistent position identifies which internally consistent position is based upon falsified GNSS carrier signals; and 
 determining navigation information based on the plurality of GNSS carrier signals not identified as falsified GNSS carrier signals. 
 
     
     
       2. The method of  claim 1 , wherein when the dither data from the characteristics of two or more of the plurality of GNSS carrier signals are highly correlated, the corresponding two or more of the plurality of GNSS carrier signals are identified as falsified GNSS carrier signals. 
     
     
       3. The method of  claim 1 , further comprising the steps of:
 detecting jitter of a vehicle; 
 temporally tracking the jitter of the vehicle, thereby creating jitter data; 
 comparing dither data with jitter data; and 
 identifying at least one falsified GNSS carrier signal based upon a degree of correlation of the dither data and the jitter data, wherein when the dither data from the characteristics of one of the plurality of GNSS carrier signals is not highly correlated with the jitter data, the corresponding one of the plurality of GNSS carrier signals is identified as the falsified GNSS carrier signal. 
 
     
     
       4. The method of  claim 3 , further comprising the step of introducing artificial jitter to the vehicle, the step of introducing artificial jitter prior to the step of detecting jitter. 
     
     
       5. The method of  claim 4 , wherein the step of introducing artificial jitter includes at least one of changing an engine speed of the vehicle, changing a speed of the vehicle, changing an altitude of the vehicle, changing a roll of the vehicle, changing a pitch of the vehicle, changing a yaw of the vehicle, changing a flight control surface of the vehicle, or changing a location or attitude of an antenna of a receiver used in the step of detecting a plurality of GNSS carrier signals with respect to a vehicle coordinate frame. 
     
     
       6. The method of  claim 1 , further comprising the steps of:
 estimating expected values for one or more characteristics of the plurality of GNSS carrier signals, thereby creating expected data; 
 detecting one or more actual characteristics of the plurality of GNSS carrier signals, thereby creating actual data; 
 comparing the expected data with the actual data; and 
 identifying at least one falsified GNSS carrier signal based upon a degree of correlation of the expected data with the actual data, wherein when the actual data is not highly correlated with a corresponding one of the expected data, the one of the plurality of GNSS carrier signals corresponding to the actual data that is not highly correlated is identified as the falsified GNSS carrier signal. 
 
     
     
       7. The method of  claim 1 , further comprising the steps of:
 determining a respective location of a transmitter corresponding to each of the at least one falsified GNSS carrier signal; 
 temporally tracking the respective location of the transmitter corresponding to each of the at least one falsified GNSS carrier signal; 
 identifying, as a stationary transmitter, each transmitter whose respective location does not temporally change; 
 identifying, as a stationary falsified GNSS carrier signal, each of the at least one falsified GNSS carrier signal corresponding to a stationary transmitter; and 
 determining navigation information based on each stationary falsified GNSS carrier signal. 
 
     
     
       8. A system comprising:
 an antenna for detecting a plurality of Global Navigation Satellite System (GNSS) carrier signals; 
 at least one processor; and 
 memory that stores instructions that, when executed by the at least one processor, cause the at least one processor to perform acts including:
 temporally tracking characteristics of the plurality of GNSS carrier signals for dither, thereby creating dither data; 
 comparing the dither data; 
 identifying at least one falsified GNSS carrier signal based upon a degree of correlation of the dither data; 
 temporally tracking the plurality of GNSS carrier signals, thereby creating signal source data; 
 filtering the signal source data to remove multipath signals; 
 binning the remaining signal source data into signal sets; and 
 determining one or more signal sets that produce a corresponding internally consistent position according to a cost function based on a consistency of a corresponding position, wherein each one of the determined signal sets corresponds to falsified GNSS carrier signals or true satellite-transmitted GNSS carrier signals; 
 wherein further processing of each of the one or more signal sets that produce a corresponding internally consistent position identifies which internally consistent position is based upon falsified GNSS carrier signals; and 
 determining navigation information based on the plurality of GNSS carrier signals not identified as falsified GNSS carrier signals. 
 
 
     
     
       9. The system of  claim 8 , wherein when the dither data from the characteristics of two or more of the plurality of GNSS carrier signals are highly correlated, the corresponding two or more of the plurality of GNSS carrier signals are identified as falsified GNSS carrier signals. 
     
     
       10. The system of  claim 8 , wherein the memory stores instructions that, when executed by the at least one processor, cause the at least one processor to perform further acts including:
 detecting jitter of a vehicle, the vehicle including the antenna; 
 temporally tracking the jitter of the vehicle, thereby creating jitter data; 
 comparing dither data with jitter data; and 
 identifying at least one falsified GNSS carrier signal based upon a degree of correlation of the dither data and the jitter data, wherein when the dither data from the characteristics of one of the plurality of GNSS carrier signals is not highly correlated with the jitter data, the corresponding one of the plurality of GNSS carrier signals is identified as the falsified GNSS carrier signal. 
 
     
     
       11. The system of  claim 10 ,
 further comprising means for introducing artificial jitter to the vehicle; 
 wherein the artificial jitter includes at least one of changing an engine speed of the vehicle, changing a speed of the vehicle, changing an altitude of the vehicle, changing a roll of the vehicle, changing a pitch of the vehicle, changing a yaw of the vehicle, changing a flight control surface of the vehicle, or changing a location or attitude of the antenna with respect to a vehicle coordinate frame. 
 
     
     
       12. The system of  claim 8 , wherein the memory stores instructions that, when executed by the at least one processor, cause the at least one processor to perform further acts including:
 determining a respective location of a transmitter corresponding to each of the at least one falsified GNSS carrier signal; 
 temporally tracking the respective location of the transmitter corresponding to each of the at least one falsified GNSS carrier signal; 
 identifying, as a stationary transmitter, each transmitter whose respective location does not temporally change; 
 identifying, as a stationary falsified GNSS carrier signal, each of the at least one falsified GNSS carrier signal corresponding to a stationary transmitter; and 
 determining navigation information based on each stationary falsified GNSS carrier signal. 
 
     
     
       13. A computer-readable storage device comprising instructions that, when executed by at least one processor, cause the at least one processor to perform acts comprising:
 detecting a plurality of Global Navigation Satellite System (GNSS) carrier signals; 
 temporally tracking characteristics of the plurality of GNSS carrier signals for dither, thereby creating dither data; 
 comparing the dither data; 
 identifying at least one falsified GNSS carrier signals based upon a degree of correlation of the dither data; 
 temporally tracking the plurality of GNSS carrier signals, thereby creating signal source data; 
 filtering the signal source data to remove multipath signals; 
 binning the remaining signal source data into signal sets; and 
 determining one or more signal sets that produce a corresponding internally consistent position, wherein each one of the determined signal sets corresponds to falsified GNSS carrier signals or true satellite-transmitted GNSS carrier signals according to a cost function based on a consistency of a corresponding position; 
 wherein further processing of each of the one or more signal sets that produce a corresponding internally consistent position identifies which internally consistent position is based upon falsified GNSS carrier signals; and 
 determining navigation information based on the plurality of GNSS carrier signals not identified as falsified GNSS carrier signals. 
 
     
     
       14. The computer-readable storage device of  claim 13 , wherein when the dither data from the characteristics of two or more of the plurality of GNSS carrier signals are highly correlated, the corresponding two or more of the plurality of GNSS carrier signals are identified as falsified GNSS carrier signals. 
     
     
       15. The computer-readable storage device of  claim 13 , wherein the acts further comprise:
 detecting jitter of a vehicle; 
 temporally tracking the jitter of the vehicle, thereby creating jitter data; 
 comparing dither data with jitter data; and 
 identifying the at least one falsified GNSS carrier signal based upon a degree of correlation of the dither data and the jitter data, wherein when the dither data from the characteristics of one of the plurality of GNSS carrier signals is not highly correlated with the jitter data, the corresponding one of the plurality of GNSS carrier signals is identified as the falsified GNSS carrier signal. 
 
     
     
       16. The computer-readable storage device of  claim 15 ,
 wherein the acts further comprise introducing artificial jitter to the vehicle; and 
 wherein the artificial jitter includes at least one of changing an engine speed of the vehicle, changing a speed of the vehicle, changing an altitude of the vehicle, changing a roll of the vehicle, changing a pitch of the vehicle, changing a yaw of the vehicle, changing a flight control surface of the vehicle, or changing a location or attitude of an antenna of a receiver used in the step of detecting a plurality of GNSS carrier signals with respect to a vehicle coordinate frame. 
 
     
     
       17. The computer-readable storage device of  claim 13 , wherein the acts further comprise:
 determining a respective location of a transmitter corresponding to each of the at least one falsified GNSS carrier signal; 
 temporally tracking the respective location of the transmitter corresponding to each of the at least one falsified GNSS carrier signal; 
 identifying, as a stationary transmitter, each transmitter whose respective location does not temporally change; 
 identifying, as a stationary falsified GNSS carrier signal, each of the at least one falsified GNSS carrier signal corresponding to a stationary transmitter; and 
 determining navigation information based on each stationary falsified GNSS carrier signal.